title: Interactions of different inhibitors with active-site aspartyl residues of HIV-1 protease and possible relevance to pepsin.
abstract: The importance of the active site region aspartyl residues 25 and 29 of the mature HIV-1 protease (PR) for the binding of five clinical and three experimental protease inhibitors [symmetric cyclic urea inhibitor DMP323, nonhydrolyzable substrate analog (RPB) and the generic aspartic protease inhibitor acetyl-pepstatin (Ac-PEP)] was assessed by differential scanning calorimetry. DeltaT(m) values, defined as the difference in T(m) for a given protein in the presence and absence of inhibitor, for PR with DRV, ATV, SQV, RTV, APV, DMP323, RPB, and Ac-PEP are 22.4, 20.8, 19.3, 15.6, 14.3, 14.7, 8.7, and 6.5 degrees C, respectively. Binding of APV and Ac-PEP is most sensitive to the D25N mutation, as shown by DeltaT(m) ratios [DeltaT(m)(PR)/DeltaT(m)(PR(D25N))] of 35.8 and 16.3, respectively, whereas binding of DMP323 and RPB (DeltaT(m) ratios of 1-2) is least affected. Binding of the substrate-like inhibitors RPB and Ac-PEP is nearly abolished (DeltaT(m)(PR)/DeltaT(m)(PR(D29N)) > or = 44) by the D29N mutation, whereas this mutation only moderately affects binding of the smaller inhibitors (DeltaT(m) ratios of 1.4-2.2). Of the nine FDA-approved clinical HIV-1 protease inhibitors screened, APV, RTV, and DRV competitively inhibit porcine pepsin with K(i) values of 0.3, 0.6, and 2.14 microM, respectively. DSC results were consistent with this relatively weak binding of APV (DeltaT(m) 2.7 degrees C) compared with the tight binding of Ac-PEP (DeltaT(m) > or = 17 degrees C). Comparison of superimposed structures of the PR/APV complex with those of PR/Ac-PEP and pepsin/pepstatin A complexes suggests a role for Asp215, Asp32, and Ser219 in pepsin, equivalent to Asp25, Asp25', and Asp29 in PR in the binding and stabilization of the pepsin/APV complex.
authors.affiliation: Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, DHHS, Bethesda, MD 20892-0520, USA.
authors.forename: Jane M
authors.initials: JM
authors.lastname: Sayer
authors.forename: John M
authors.initials: JM
authors.lastname: Louis
mesh_terms: D000069446:Atazanavir Sulfate; D001665:Binding Sites / Q000235:genetics; D001667:Binding, Competitive; D002152:Calorimetry, Differential Scanning; D002219:Carbamates / Q000737:chemistry / Q000378:metabolism; D018360:Crystallography, X-Ray; D000069454:Darunavir; D005663:Furans; D016333:HIV Protease / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017320:HIV Protease Inhibitors / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D019469:Indinavir / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D061466:Lopinavir; D008958:Models, Molecular; D015394:Molecular Structure; D009154:Mutation; D019888:Nelfinavir / Q000737:chemistry / Q000378:metabolism; D009842:Oligopeptides / Q000737:chemistry / Q000378:metabolism; D010434:Pepsin A / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011725:Pyridines / Q000737:chemistry / Q000378:metabolism; D011744:Pyrimidinones / Q000737:chemistry / Q000378:metabolism; D011753:Pyrones / Q000737:chemistry / Q000378:metabolism; D019438:Ritonavir / Q000737:chemistry / Q000378:metabolism; D019258:Saquinavir / Q000737:chemistry / Q000378:metabolism; D013449:Sulfonamides / Q000737:chemistry / Q000378:metabolism
chemical_list: D002219:Carbamates; D005663:Furans; D017320:HIV Protease Inhibitors; D009842:Oligopeptides; D011725:Pyridines; D011744:Pyrimidinones; D011753:Pyrones; D013449:Sulfonamides; D061466:Lopinavir; D000069446:Atazanavir Sulfate; C095108:amprenavir; D019469:Indinavir; D016333:HIV Protease; C514803:p16 protease, Human immunodeficiency virus 1; D010434:Pepsin A; D019888:Nelfinavir; D019258:Saquinavir; D019438:Ritonavir; D000069454:Darunavir; C107201:tipranavir